Prompt constraints are the explicit limits, rules, or conditions that shape how a model should complete a task. They tell the model what boundaries matter, not just what outcome is wanted.
Why it matters
Constraints are one of the main reasons a prompt becomes reusable. In Promptlight, they help separate a reliable workflow from a vague request that happened to work once.
Example in practice
A research synthesis prompt might include constraints like:
- use only the provided notes
- keep findings under five bullets
- separate evidence from recommendation
- do not infer intent without support
Those limits make the output easier to review and less likely to drift.
What to look for
Strong constraints usually do one or more of these:
- narrow the evidence the model can use
- define what should be avoided
- set output boundaries
- control the level of confidence
- protect readability or safety
Constraints are most useful when they are testable. “Be smart” is not a constraint. “Do not make claims unsupported by the source notes” is.
Common confusion
Prompt constraints are not the same as objective execution mode or output contracts.
- Objective Execution Mode sets tone and operating bias.
- Constraints define limits and acceptable behavior.
- Output Contract defines the expected structure of the answer.
Related context
Constraints work especially well with Hallucination Guardrails. For practical use, continue with Use Objective Execution Mode Safely and Review Objective Execution Prompts Before Sharing.